Hybrid configurations for brackish water desalination: a review of operational parameters and their impact on performance

ABSTRACT

The remote villages in arid and semi-arid inland regions of Rajasthan state in India and many other countries are dependent on brackish groundwater for potable uses. Generally, community RO (Reverse Osmosis) plants are installed for brackish water treatment in rural agglomerations where the MLD (Minimal liquid discharge) scheme is followed which includes pre-treatment and pre-concentration technologies, that consumes relatively low energy than thermal technologies for ZLD (Zero liquid discharge). This paper discusses the application of hybrid processes involving MLD technologies such as IEX (Ion Exchange), NF (Nanofiltration), RO, FO (Forward Osmosis) and UF (Ultrafiltration). for brackish water treatment. The impact of feed water quality and operational parameters such as flux, feed flow rate and transmembrane pressure are discussed. Further, performance indicators such as salt rejection, recovery, energy consumption and scaling propensity are discussed to evaluate the feasibility of various configurations. The findings of this review indicate NF as impressive membrane technology for conjunction with IEX, RO and UF. Further, the use of FO or NF as a pre-treatment for RO has been found to reduce the scaling propensity of RO membranes; and the use of UF as a pre-treatment for NF has been found to reduce the propensity of organic fouling on NF membranes. Also, IEX as a pre-treatment can be coupled with low-pressure RO/NF to remove the scale-causing divalent ions and enhance recovery along with an option of reusing RO/NF reject water for regeneration of IEX column.

GRAPHICAL ABSTRACT

KEYWORDS:

• Ion-exchange
• nanofiltration
• reverse osmosis
• forward osmosis
• hybrid desalination

Acknowledgements

This work was undertaken as a part of the project titled ‘Development of integrated treatment scheme for RO reject management’. The authors are thankful to the WSSO (Water and sanitation support organization), PHED (Public Health and Engineering Department), Government of Rajasthan (India) for funding this project.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

Data sharing is not applicable to this article as no new data were created or analyzed in this study.

Additional information

Funding

This work was supported by Water and Sanitation Support Organisation (WSSO), Government of Rajasthan, India [http://dx.doi.org/10.13039/100013646].

Notes on contributors

Kanika Saxena

Kanika Saxena is working as a Research Associate in Malaviya National Institute of Technology Jaipur. She has PhD and Masters Degree in Environmental Engineering and Bachelors in Civil Engineering. She has worked in the area of water/wastewater treatment, textile wastewater treatment and membrane processes.

Urmila Brighu

Urmila Brighu is a professor in the civil engineering department at Malaviya National Institute of Technology Jaipur. She has a bachelor degree in civil engineering and master degree in environmental engineering. She did her PhD from Cranfield University. She has years of experience in water and wastewater treatment. She has worked on wetlands, textile waste treatment and is presently working on enhanced coagulation.

Sakshi Jain

Sakshi Jain has a Masters degree in Environmental Engineering. She has worked on membrane processes.

Akash Meena

Akash Meena has a Masters degree in Environmental Engineering. He has worked on membrane processes.